Hypoxia Reduces Arylsulfatase B Activity and Silencing Arylsulfatase B Replicates and Mediates the Effects of Hypoxia

Department of Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America.
PLoS ONE (Impact Factor: 3.53). 03/2012; 7(3):e33250. DOI: 10.1371/journal.pone.0033250
Source: PubMed

ABSTRACT This report presents evidence of 1) a role for arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase) in mediating intracellular oxygen signaling; 2) replication between the effects of ARSB silencing and hypoxia on sulfated glycosaminoglycan content, cellular redox status, and expression of hypoxia-associated genes; and 3) a mechanism whereby changes in chondroitin-4-sulfation that follow either hypoxia or ARSB silencing can induce transcriptional changes through galectin-3. ARSB removes 4-sulfate groups from the non-reducing end of chondroitin-4-sulfate and dermatan sulfate and is required for their degradation. For activity, ARSB requires modification of a critical cysteine residue by the formylglycine generating enzyme and by molecular oxygen. When primary human bronchial and human colonic epithelial cells were exposed to 10% O(2) × 1 h, ARSB activity declined by ~41% and ~30% from baseline, as nuclear hypoxia inducible factor (HIF)-1α increased by ~53% and ~37%. When ARSB was silenced, nuclear HIF-1α increased by ~81% and ~61% from baseline, and mRNA expression increased to 3.73 (± 0.34) times baseline. Inversely, ARSB overexpression reduced nuclear HIF-1α by ~37% and ~54% from baseline in the epithelial cells. Hypoxia, like ARSB silencing, significantly increased the total cellular sulfated glycosaminoglycans and chondroitin-4-sulfate (C4S) content. Both hypoxia and ARSB silencing had similar effects on the cellular redox status and on mRNA expression of hypoxia-associated genes. Transcriptional effects of both ARSB silencing and hypoxia may be mediated by reduction in galectin-3 binding to more highly sulfated C4S, since the galectin-3 that co-immunoprecipitated with C4S declined and the nuclear galectin-3 increased following ARSB knockdown and hypoxia.

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    ABSTRACT: In this report, the gene regulatory mechanism by which decline in arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase) reduces CHST11 (chondroitin-4-sulfotransferase; C4ST) mRNA expression in human colonic epithelial cells and in colonic epithelium of ARSB-deficient mice is presented. ARSB controls the degradation of chondroitin 4-sulfate (C4S) by removing the 4-sulfate group at the non-reducing end of the C4S chain, but has not previously been shown to affect C4S biosynthesis. The decline in CHST11 expression following ARSB reduction is attributable to effects of ARSB on bone morphogenetic protein (BMP)4, since BMP4 expression and secretion declined when ARSB was silenced. Inhibition of BMP4 by neutralizing antibody also reduced CHST11 expression. When C4S was more sulfated due to decline in ARSB, more BMP4 was sequestered by C4S in the cell membrane, and CHST11 expression declined. Exogenous recombinant BMP4, acting through a phospho-Smad3 binding site in the CHST11 promoter, increased the mRNA expression of CHST11. In contrast to the decline in BMP4 that followed decline in ARSB, Wnt9A mRNA expression was previously shown to increase when ARSB was silenced and C4S was more highly sulfated. Galectin-3 bound less to the more highly sulfated C4S, leading to increased nuclear translocation and enhanced galectin-3 interaction with Sp1 in the Wnt9A promoter. Silencing Wnt9A increased the expression of CHST11 in the colonic epithelial cells, and chromatin immunoprecipitation assay demonstrated enhancing effects of Wnt9A siRNA and exogenous BMP4 on the CHST11 promoter through the pSmad3 binding site. These findings suggest that cellular processes mediated by differential effects of Wnt9A and BMP4 can result from opposing effects on CHST11 expression. Copyright © 2014. Published by Elsevier B.V.
    Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms 12/2014; 1849(3). DOI:10.1016/j.bbagrm.2014.12.009 · 5.44 Impact Factor
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    PLoS ONE 07/2014; 9(7):e102483. DOI:10.1371/journal.pone.0102483 · 3.53 Impact Factor
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